Death Star- Prison Break
Once it was finally finish, the Death Star, was the Emperor's favorite toy. It was also the most boring assignment in the galaxy for a stormtrooper. Tedious inspection drills, endless hours of guarding impregnable force shield generators. Even Cutter who likes to take it slow misses the action. Headshot couldn't take it anymore; he was obviously slowly getting insane. Things got so bad that, when a prison break erupted in the cells block, we were almost happy to have someone shooting at us again. If only we'd known what an embarrassing snipestorm we were about to wade into, we probably would of jettisoned the whole detention block into space. We should of, but we were blinded by our ego, finally having something to do. The only good thing that happing was that it calms Headshot down by quite a lot. We were all afraid to be force to put him down. At first, they badly straggle to take over the station but it was all a trick. They organize everything. They forced us to leave the hangers wide open by chasing then at the other end at the main canon. We took all our force to take it back so they couldn't make damage to it. But while they distracted us, the prisoners took the plans of the Death Star, took the ship that the inspection crew brought. We got fooled badly, we have no excuse. It was our pity downfall, but not our end. They actually made a copy of the plans so we would be chasing the wrong person. Thankfully, we destroyed the ship they hijacked but the plan was beam out of the station. If some of the prisoners would have escaped without the plan, our commander would have been fine with it but the plan was out in the open within our enemies hands. Worse of all, a Jedi had somehow getting into the station and created the riot itself. We have killed the Jedi making sure we would be no trouble, but celebration was not in our minds. Not after what happen. After the embarrassment of the prison break, Lord Vader removed us from our comfortable billet, and began dragging the 501st across the galaxy in a dangerous hunt for the now-missing Death Star planed. Ironically, our punishment eventually proven to be our salvation; the poor souls who took our place in the detention area were completely wiped out when the Death Star was destroyed.
So that is how the rebels got the plans. They never really explained how they obtained it. Even if they were the bad guys, they been to a lot.